Slurs
It would be very useful to have straight line slurs available. They feature a lot in Scottish music, especially in strathspeys. I improvise using the horizontal straight line from the lines menu but it requires tedious manipulation to put it in place.
Comments
Meanwhile (with the help of google translator):
Select the note and press S insert the slur, you can adjust the handles (maybe it's faster?)
Two links below refer to slurs that are predominately straight lines, but with curved ends. Is this what you mean?
Regarding flat slurs, such as:
https://musescore.org/en/node/56166
an issue was filed:
https://musescore.org/en/node/56446
If you want a slur to become a straight line (without curved ends), it can be done by double clicking on the slur and dragging the center handle to make the curve flat - as previously mentioned.
See attachment.
Regards.