Since v2.7.0
Available on all platforms
See also

The SHOW function makes visible some levels of the stack which were previously hidden by a call to HIDE.

The levels made visible are the ones closest to the top of the stack. Depending on the levels parameter to the call to SHOW, the revealed levels could be the whole stack (levels == 0), a maximum number of levels (levels > 0) or a number of levels such that there are at most a certain number ((abs(levels)) with levels < 0) of visible levels after the call.