click on gradient line to add stop

[Michael Maier]

If you "Create and edit gradients" and you hover with the mouse cursor over the gradient line (no stop) then "+" is shown on the lower-right side of the cursor. This makes you think that you can add a stop by a simple click. However, you have to additionally press Ctrl+Alt to do so. Otherwise, you loose the selection of the gradient/object. This is counterintuitive.

I suggest to either insert a new stop by a simple click (without pressing Ctrl+Alt) on the gradient line or to show "+" only if you press Ctrl+Alt while showing a hint for this shortcut in the footer when you do a hover without pressing Ctrl+Alt. A similar hint "click with Ctrl+Alt to delete stop" is already shown if you hover over a stop on the gradient line.

[su_v (suv-lp)]

New gradient stops can be added in the gradient tool context by double-clicking (LMB) the gradient line. This is a known interaction - it is the same to insert a new node into a path segment when using the node tool (which also supports the alternative 'Ctrl+Alt' LMB single click action to insert a new node).

The current selection in the gradient tool context is indeed lost when inserting a gradient stop with a double-click if the gradient line is over an empty canvas area - this particular issue is tracked in
* Bug #1288486 “double clicking on a gradient line without a shape under it, deselects the gradient shape”
  https://bugs.launchpad.net/inkscape/+bug/1288486