How to get rid of a left sidebar with "1 2" at the top and + or - below which collapses some rows?

On the left I have some bar appear on my 1st tab only, at the top it has a 1+2 box and down at row 34 it has a + which when clicked turns into a -

When I click - the row 34 disappears and when I click + it shows again so it’s something to do with that row. the 1+2 do the same as the + & -

been frustrating me for so long, can’t work it out. Let me know if you know how to get rid of this!

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Please just press Ctrl+F12

@JohnSUN, Thanks! Interesting.

Caution: On Linux w/ Cinnamon if I press Ctrl-Fn-F12 my screens all go black. (This selects an alternate TTY.) Ctrl-Fn-F7 restores then. Instead you want simply Ctrl-F12.

Also note that if you Ungroup while a ‘-’ (minus) is present and some rows are hidden it gets locked in. If this happens group, then change to +, then ungrouping.

I love you man, ty.