Type the range in the Search field (e.g 20-50) and press Enter or click PR source button above the field). The Enter key for ranges works if you have "Project source segments" selected as the default scope in the Find panel.
Would it be possible to enable multiple ranges for selection? 33-39,42-45 etc.
Or perhaps the equal sign (for: right=left), if this doesn't interfere with your code.
While we're at it (at least: I am): would it be possible to add some modification actions to perform on the selected segments?
First one that comes to mind (at least to mine) is: toggle case.