As many have, this bug was first noticed quite a few years back (~2010). This bug is essentially when click one toolbar, then going to another area of the application, the window focus is not being correctly updated. This currently affect GIMP 2.8.22 (occasionally in multiwindow, frequently in single-window-mode) and Inkscape 0.92.2, making them practically unusable. These were once working really well, but now I tend to avoid them when I can.
I have searched many sources and they all lead to inconclusive bug reports or reports that a fix is not in the making.
I know of this issue, Is there a way to fix gimp on OSX to solve the xwindows focus issue? However, that is different since for that case, single-window-mode is a functioning workaround, but it does work.
More bug reports:
I am not sure if this MS Windows specific, but I can confirm this bug on some Win7 and Win10 PCs. However, in one of the reports, it seems some linux users were affected as well.
Can anyone shed some light on this? Is there a fix or workaround? Or is there theory as to why this is happening?
I have resorted to using an old version of inkscape (v0.48.2). It works just fine on my home laptop (Win10) and work laptop (Win10). No window focus bug. Only 32 bit version is offered... could it be something with x64? I'll have to test that.
This seems to be fixed in GIMP v2.9.8 (devel). https://www.gimp.org/downloads/devel/