RubyMine allows bookmarking lines of code. This is super-helpful when working on a complex problem.
I've been using this feature for a few years now, and so should you! :)

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Read more Show archive.org snapshot

Here are the default Linux/Windows keystrokes. See the documentation Show archive.org snapshot for other keybindings.

Add an anonymous bookmark

F11

A gray checkmark will be shown in the gutter on the left.
If you press F11 again on a bookmarked line, the bookmark will be removed.

Add a named bookmark ("mnemonic")

Ctrl + F11

This will show a popover with digits and letters. Simply press the corresponding key to assign it to that bookmark.
The chosen mnemonic will be shown instead of the checkmark.

I recommend using mnemonics, at least with digits, instead of anonymous bookmarks. That way you can later reconstruct the way you came.

List bookmarks

Shift + F11

Shows a list if all bookmarks, and a small preview panel. You can navigate using the up/down arrow keys.
Reordering works by pressing Ctrl + up/down arrow keys; press Delete to remove a bookmark.

Go to named bookmark

Shift + F11, then the assigned key