Yep I reproduced this with a M510 mouse. After enabling the mouse buttons (I never use them) and starting xbindkeys I see that my forward and backward thumb buttons work in Firefox (did not before these steps):
And these thumb buttons have no effect in the Libreoffice save dialog. But they don't seem to have an effect in any save dialog.. I also tried various save dialogs in: firefox, gimp, gedit.
Yep I reproduced this with a M510 mouse. After enabling the mouse buttons (I never use them) and starting xbindkeys I see that my forward and backward thumb buttons work in Firefox (did not before these steps):
$ sudo apt install xvkbd xbindkeys
$ cat ~/.xbindkeysrc
# Mouse Buttons
"xvkbd -xsendevent -text "\[XF86Back]""
m:0x0 + b:8
"xvkbd -xsendevent -text "\[XF86Forward]""
m:0x0 + b:9
$ xbindkeys
And these thumb buttons have no effect in the Libreoffice save dialog. But they don't seem to have an effect in any save dialog.. I also tried various save dialogs in: firefox, gimp, gedit.
So I think this is a gnome dialog issue.