[Qgis-user] Modeler: point input from clicked coordinates

[Thomas Schüttenberg]

Hi!
Just started with QGIS (3.4) modeler and stumbled across a - hopefully simple - question: how to input a point (coordinates) picked by a mouse click?

When using the shortest path (point to point) alg direct from the processing toolbox I have the oportunity to pick start and end points with a mouse-click after clicking the button with the three dots [...]; the window moves aside and the mouse cursor turns into a crosshair for picking. -  So far, so good.

But when using this algorithm in a model the mentioned button doesn't work like this: the window minimizes, but the cursor keeps beeing an arrow and does not pick a coordinate/point. 
My input parameter for start and end is 'point' with no default defined.

Any hint and help appreciated, thanks.

Thomas