Here's the log from start of the tool without logging in. I replaced user name with *** in the log and cut out the connection info, but you can still see where the most time is spent.
PL/SQL Developer
Version 12.0.7.1837 (64 bit)
Windows 7 Build 7601 (Service Pack 1)
Physical memory : 8 283 168 kB (3 207 020 available)
Paging file : 16 669 916 kB (11 214 336 available)
Virtual memory : 8 589 934 464 kB (8 589 688 260 available)
Parameters
C:\Program Files\PLSQL Developer 12\plsqldev.exe
DebugSQL
Preferences
Session mode: Multi
OCI Library:
Use OCI7: False
Allow Multiple Connections: True
Preference Files
Debug file
C:\Users\***\AppData\Roaming\PLSQL Developer 12\PlSqlDev.elf
Plug-Ins
Process
Working Set = 108 802 048
Memory = 43 707 664
GDI Objects = 351
User Objects = 214
Handles = 153
Monitor
PixelsPerInch = 96
Id = 0
Primary = True
Handle = 65537
Left = 0
Top = 0
Width = 1920
Height = 1080
MainFormOnTaskbar = False
09.03.2018 13:20:12 Debug started
00:00:00.003 InitPreferences
00:00:00.003 Load C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\default = 0
00:00:00.004 PreferenceSet.Load C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\default\Default.ini
00:00:00.004 PreferenceSet.Load OK
00:00:00.005 Determine LocalPrefPath
00:00:00.005 [1]: C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences
00:00:00.007 LocalPrefPath: C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\***
00:00:00.007 Load C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\*** = 0
00:00:00.008 PreferenceSet.Load C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\***\default.ini
00:00:00.008 PreferenceSet.Load OK
00:00:00.009 PreferenceSet.Load C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\***\user.prefs
00:00:00.011 PreferenceSet.Load OK
00:00:00.011 InitPreferences end
00:00:00.012 SortPreferenceSets
00:00:00.012 - Default ***
00:00:00.013 - System Default
00:00:00.147 UpdateConnections
00:00:00.147 UpdateConnectionsChildList start
00:00:00.147 UpdateConnectionsChildList ConnectionFolders.Count = 1
00:00:00.148 UpdateConnectionsChildList CheckList.Count = 1
00:00:00.148 UpdateConnectionsChildList RemoveList.Count = 0
00:00:00.148 UpdateConnectionsChildList EndUpdate
00:00:00.149 UpdateConnectionsChildList end
00:00:00.149 DoUpdateChildList starts
00:00:00.169 Lock
00:00:00.170 UnLock
00:00:00.170
00:00:00.170 09.03.2018 13:20:12 Debug stopped
00:00:00.171
00:00:00.270 pfReadRegistry(PL/SQL Developer 12\Shell\Open\Command, )
00:00:00.270 ReadString Faled
00:00:00.271 pfReadRegistry:
00:00:00.271 CalculateToolbarGlyphs (DPI = 96)
00:00:00.271 CalculateToolbarGlyphs done
00:00:00.449 Splash: Starting PL/SQL Developer 12
00:00:00.450 Splash: Version 12.0.7.1837 (64 bit)
00:00:00.451 LoadPreferences
00:00:00.451 LoadPreferences searching for default
00:00:00.452 C:\Users\***\AppData\Roaming\PLSQL Developer 12\Preferences\***\default.ini
00:00:00.452 LoadPreferences NewPref := nil
00:00:00.452 LoadPreferences
00:00:00.453 LoadPreferences Reading preferences
00:00:00.453 Splash: Reading preferences
00:00:00.463 FormResize
00:00:00.472 FormResize
00:00:00.474 LoadPreferences ReadPosition
00:00:00.496 FormResize
00:00:00.561 LoadPreferences ToolsBrowserItemClick(nil)
00:00:00.561 LoadPreferences CreateBrowserFilters...
00:00:00.563 LoadPreferences Files
00:00:00.563 LoadPreferences Printer
00:00:00.564 LoadPreferences FileBrowserFolders
00:00:00.564 LoadPreferences Connections
00:00:00.565 LoadPreferences BrowserFolders
00:00:00.566 LoadPreferences
00:00:00.566 LoadPreferences end
00:00:14.203 MacroLibFilename: C:\Program Files\PLSQL Developer 12\Macro\***.emlib
00:00:14.303 Splash: Reading keywords
00:00:14.304 GetRootFile: C:\Users\***\AppData\Roaming\PLSQL Developer 12\default.kwf
00:00:14.315 Logging on..
00:00:14.315 Creating new session
00:00:14.315 Initializing new session
00:00:14.316 Setting new session parameters
00:00:14.317 Setting logon session
00:00:14.317 OCI Initialization starts
00:00:14.319 OCI Initialization done
00:00:14.319 OCIDLL forced to C:\oraclient12\x64\oci.dll
00:00:14.320 Logon2 starting
00:00:14.320 Logon2.Execute starts
00:01:22.387 Logon2.Execute done
00:01:22.389 Logon2 done
00:01:22.390 FormCreate Logon.Executed 0
00:01:22.391 FormCreate SessionChanged
00:01:22.411 SessionChanged SetDBAViews
00:01:22.412 SessionChanged Authorizations.Load
00:01:22.412 SessionChanged EnableAuthorizedMenus
00:01:22.413 WindowAllowed(1)
00:01:22.413 WindowAllowed done
00:01:22.414 WindowAllowed(1)
00:01:22.414 WindowAllowed done
00:01:22.415 ExecuteConnectScript starts
00:01:22.415 ExecuteConnectScript ends
00:01:22.443 SessionChanged LoadRecentObjects
00:01:22.444 SessionChanged Logoff secondary sessions
00:01:22.444 SessionChanged
OCIDLL forced to C:\oraclient12\x64\oci.dll
00:01:22.445 SessionChanged Notify children
00:01:22.445 SessionChanged EnableChildFunctions
00:01:22.446 Lock
00:01:22.446 UnLock
00:01:22.446 UpdateChildList starts
00:01:26.689 FormResize
00:01:31.377 ReadTemplateFiles C:\Users\***\AppData\Roaming\PLSQL Developer 12\Template
00:01:31.672 ReadTemplateFiles Done
00:01:31.688 SortPreferenceSets
00:01:31.688 - Default ***
00:01:31.689 - System Default
00:01:31.787 Lock
00:01:31.787 UnLock
00:01:31.801 UpdateConnections