This reverts commit bede4d320b.
As JMarc notes [1], if we replaced show with toggle, we would lose some
functionality:
There is one use that is not possible with this change (as I argued
before), which is a fully keyboard-based navigation.
With LyX 2.1, I can do C-M-o and navigate with cursor in the
outline. I can do the same with advanced S&R. IN this sense,
toggling is a step back IMO.
The plan now is to find another way to close the dialog (without
using toggle), such as having ESC close it or another key bind.
Ticket #8388 will stay closed because 'show' and 'toggle' are too
close for the cost of having two separate bindings.
[1] http://www.mail-archive.com/lyx-devel@lists.lyx.org/msg187693.html
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