Grace note appoggiaturas

I have just begun using MuseScore and so far am impressed with the results. However I have come accross one glitch: the inability to control the duration of grace notes, in particular appoggiaturas. I have read various discussions on this matter together with responses, however the issue remains unresolved as far as I can tell. While there may be a rule of thumb that appoggiaturas last between 50 and 75% of the length of the main note, there are instances, for example in a slow movement of baroque music where the main note is long, say in the middle of a passage (not approaching a cadence), where the duration of the grace note should be shorter - perhaps a third of the value of the main note or less - and the 50% to 75% rule does not therefore apply.

In short, it would be helpful for the user to be able specify the duration of the appoggiatura (value of course to be deducted from the main note) which the feature in Musescore seems to suggest is possible and indeed is reflected in the score, but not playback. I appreciate the length of the appoggiatura relative to the main note depends on context, and not the written value of the note, however it would help immensely if a feature to control duration relative to the main note for playback purposes could be added.

As it stands the different values Musiscore offers for appoggiaturas all give the same result during playback regardless of which note value is selected, which can result in distorting the music in playback. To give an example, in a piece of music I am editing (a slow movement - speed 80 bpm) on adding an appoggiatura before the main note - a dotted crotchet - I would like the appoggiatura to last a third of the length of the main note, ie a quaver, but regardless of the value I select for the grace note (whether a semi quaver, quaver, crotchet etc) the appoggiatura plays for around two thirds the value of the main note. I realise it is possible to add a plugin to give more flexibility, but I use a Macbook and not sure the plugin is compatible. This playback feature isn't essential, but would make for more accurate rendition of scores and enhance the suitabiity of Musescore for different musical styles. Lastly my appologies if there is a solution which I, as a novice, have yet to discover (and I don't mean acciaccatura which occur before the beat and are something else entirely (though some folk may want to be able to specify the length of those in playback too). Thank you