I'm facing the issue that when in the SQL editor window, the [Home] and [End] button on the keyboard do not work at all.

[PageUp] and [PageDown] do work correctly.

This is quite annoying - is it related to a specific setting in the preferences ? there is no other software on that PC where I'm having the same issue

Can you go to Tools > Preferences > Key configuration and check if "Editor: Start of Line" and "Editor: End of Line" are assigned? If they are not, assign the Home and End key.

Well, that screen looked empty in the assignments which I guess is explaining why it wasn't working. I now clicked on the 'restore defaults' button and many keys have now been assigned and it seems to be working fine again.

Do you know any reason why all assignments could have been set to blank ? I've not blanked them out manually and it's a quite new fresh installation on the PC so was wondering how come ... ?

This may be a bug. Which PL/SQL Developer version are you using?

Version 7.1.5.1398 02.54469

I have the same issue a little now and then.
Reset the keys allways help.

Ver. 7.1.5.1398 01.48721

As I have several custom shortcuts, I've never tried the "restore defaults", but restarting PLSD also solves the problem.