I understood what you were asking for Jean, based on your first Post and its attached screen-capture.*
When I was more actively drafting (almost entirely 2D, architectural), I too often wished there was a way to multi-select the objects to be "trimmed out". I haven't found a way. Maybe someone has a creative solution.
*[It seems that you are: activating the Object Trim tool; holding down the Shift-key to select both the red lines, defining them as the "cutting boundary"; and individually clicking on each blue line, that portion of each that lies between the red lines. It is the individually clicking procedure that you wish to instead do in one action.]
Note: Seems that in recent versions-- such as in my version-20-- there are two trim Commands/Tools: "Object Trim" & "Trim". Both being very similar. In my installation, the "Trim" Command/Tool does not allow for selection of multiple cutting edge objects. Just a note... so that we don't confused as to what Command/Tool we are talking about.
« Last Edit: July 24, 2016, 09:33:41 AM by Alvin Gregorio »
(mostly Residential Architectural 2D; no formal CAD Training; intermittent TurboCAD user since yr. 2000 [ver6.5])
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)