They’re right there in the top-left corner of the Axure RP UI*—but have you ever clicked on them? I’m referring, of course, to the cursor selection modes: intersected and contained.
“Intersected” is the default, so it’s probably the behavior you’re familiar with: click-drag on the canvas to draw your selection box, and anything touched by the box will be made part of your selection. It’s a handy wrist-saver.
But “contained” mode is a hidden (in plain sight) gem of a feature that has become the preferred default selection behavior for many an expert user. In this mode, only the widgets entirely encompassed by your selection rectangle will be part of your selection. Use this mode when you’ve got widgets in close quarters or on top of one another and you want to select them with surgical precision but without fussing over it.
In my animation, above, I demonstrate changing modes via the main toolbar, but selection modes are the type of thing that really lend themselves to a good keyboard shortcut. So if you’re a hotkey type of person, or if you’d like to become one, try switching to the “intersected” and “contained modes using the [CTRL] +  and [CTRL] +  key combos, respectively. (Or [CMD] +  and [CMD] +  if you’re on macOS.) Welcome to the power user’s club!
*On the Mac version, anyway. The default layout of the Main Toolbar on the Windows version of Axure RP features the “save”, “load”, and a few other controls to the left of the cursor controls.