To add a measure to the end of the piece, press Ctrl+B (Mac: ⌘+B), or from the menu choose Create → Measures → Append Measure. To add multiple measures, press Ctrl+Shift⇑+B (Mac: ⌘+Shift⇑+B) or use the menu Create → Measures → Append Measures....
Select a measure, then press Ins or use the menu Create → Measures → Insert Measure to insert a new empty measure before the selected one. To insert multiple measures, press Ctrl+Ins (Mac: ⌘+Ins) or use the menu Create → Measures → Insert Measures....
Select the measure, then press Ctrl+Del (Mac: ⌘+Fn+Backspace).
To edit the properties of a measure, right-click on an empty part of the measure and select Measure Properties....
The Visible property allows you to show or hide the notes and staff lines for the current measure. The Stemless property allows you to show or hide all note stems for the current measure. Notes that normally have a stem such as half notes (minums) and quarter notes (crotchets) only show the note head when marked as stemless.
The Nominal duration is the time signature that is displayed on the score. You can change the Actual duration of a measure to anything regardless of the time signature displayed on the score. Normally, the nominal and actual duration of a measure is identical. However, a measure (e.g. pickup, anacrusis) can have an actual duration that is shorter.
In the figure below, the quarter note (crotchet) pickup has a nominal measure duration of 4/4, but an actual duration of 1/4. The measures in the middle have both nominal and actual durations of 4/4. The complimentary measure with only a dotted half note (dotted minim) at the end has an actual duration of 3/4.
An "irregular" measure is not counted in the measure numbering. Normally a pickup measure is marked as "irregular".
Add to measure number
You can also use the "add to measure no." option to influence the measure numbering. You can enter positive or negative numbers here. Please note that this affects subsequent measures. A value of "-1" has the same effect as marking a measure irregular.
You can increase, or decrease horizontal space between notes with this option.
If the measure is the end of a repeat, you can define how often it is played.
Break multi-measure rests
This property separates a multi-measure rest at the current measure. This option should be checked before you turn on the "Create multi-measure rests" option in Style → Edit General Style.
Multi-measures are automatically broken at important breaks, such as rehearsal marks, time changes, double bar lines, etc.
MuseScore automatically numbers the first measure of each system, but more numbering options are possible. From the main menu, choose Style → Edit Style. In the left pane, choose "Numbers". In the bottom half of the right pane is the "Measure Numbers" ("Bar Numbers") section.
Mark the checkbox next to the "Measure Numbers" ("Bar Numbers") to turn on automatic measure numbers.
Mark "show first" if you want the first measure numbered.
Mark "all staffs" if you want numbers on all staffs. Otherwise, only the top staff of each system shows measure numbers.
Choose to show numbers on "every system" which numbers the first measure of each line, or show numbers by "interval" and specify the size of the interval. For example, an interval of 1 numbers every measure; an interval of 5 numbers every fifth measure.