Ok, it's fine... I got it now, there is 3-4 possible select with right-click menu
1) Right click on the signal name region gives pop-up like in SigName.jpg (adding signal/clocks)... left click on a signal + right click => nothing different
2) Left click on the waveform but not on edges + right click => allows to have the "select" pop-up (WaveForm1.jpg)
3) When the waveform "selected", signal/shape can be edited => WaveForm2.jpg
4) When selecting a waveform edge, another right-click popup appears => Edge.jpg
Perhaps left+right click on a signal name (like SigName.jpg) could select it in order to:
- edit value (freq, duty cycle etc)
- or suppress it
- or change its shape (line, space, move signal sig up/down)