Is it possible within the web interface or the connect android interface or wathever where
to create an extra lap ? for example chose a specific Km and see all inffo on that specific km ?
Yes but if you look at polar... so much advanced !
you select a part of the workout and for the selected part, you have Min HR max HRAverge...
then also the zones for the selected part..... the easiest part, is the first screenshot !! avg min max hr power rpm....


I haven't really been following any changes to Garmin Connect for the past nine months or so, but simply kept using it as I did before for the occasional run, but I don't think Garmin's apparent philosophy has changed.
Garmin Connect is not provided as,or designed to be, a tool for after-the-fact analysis of activity data. All the 'smarts', including things that some users think are as 'basic' as cumulative time in heart rate zones, are done only on the recording device and form part of the activity record; no post-processing is done after the record has been synced to GC's central server(s) and made available for the user to retrieve and review. No breaking out arbitrary subsets of data for 'zooming in' or summaries; it's the whole thing as recorded, laps as recorded, or individual data points as recorded.
If you want any other sort of analytical capability over the recorded data, you'll have to get it elsewhere — and it seems you know just where to get it. Being able to export-transfer-import the data to other tools, and the cost and inconvenience of it, is not a concern to Garmin.