I think you want to make labeling the cables on your project auto numbering:
Click in Configure on the folio (page) properties section>auto numbering>conductor tab
Another way is Project properties>auto numbering>conductor tab
Name of the new numbering starting by L1 name (ex: configure one by one for each L1, L2 and L3 name)
Select type text and fill to "L1-" value
After this, click add (+) above value label
select number and fill to "1" value (here is the auto increment)
Click Apply and ok button ad return to folio
Go to properties section>select your desired conductor name
Test your wire connection with your elements
Tip: Keep in mind that the auto numbering is a sequence, if want to restart i do recommend to fill 1 value or another to new sequence on the properties of conductors again.
I hope helps You!