Ability to create tuplet with total duration different of note figure

Currently, you need to select a rest or a note to create a tuplet. This note is then used as the total duration of the tuplet.
So, it's not possible to create a tuplet of 6 8th notes on the duration of 5 8th notes since there is no way to select a note/rest of 5 8th notes. The file format is apparently able to deal with this.

Proposition:

• Modify other tuplet dialog and add a "base value" or something to say X something in the time of Y something, with X, Y and something changeable
• Tuplet will be inserted in the voice and at the tick position of the selected rest/chord, and span on the duration Y*something (Nothing happens, if the total duration goes over the measure. All existing chords/rests on the total duration are removed)

Workaround for the time being : Create a measure with actual duration the total duration, select the rest and create the tuplet. You can copy paste the resulting tuplet.