I'm new to this and I haven't found this menu at the left-side of the program. I accidentally press the

X

on the tab. What tab? The tab where you can choose paint bucket, free draw, Text box, Square, Circle, pointer, and that's pretty much all I remember. Hopefully anyone reading this could understand and help me!

try settings>dockers>toolbox

you should be able to get it back like this:

Settings → Dockers → Toolbox

Thanks, both of you!