Shift+click a range of measures and it loops
Picking a range of measures with Shift+click (or a long-press, then a tap, on a phone) now turns looping on, so there's no loop button to press afterwards.
To practise a passage, click its first measure and Shift+click its last. Looping now turns on by itself, and the line under the score says which measures loop. If the song is playing, it jumps to the start of the range and loops it straight away.
On a phone or tablet, long-press the first measure and tap the last. Ctrl+click (Cmd+click on a Mac) works too.
To stop looping, press the loop button at the end of the range. A plain click on one measure still just moves playback there. While the tab editor is open, Shift+click selects notes to edit as before and leaves looping alone.