The Electron had a new enough version of BBC Basic that "proper" procedures and UDFs were supported (in a limited fashion, but well enough considering the constraints of the machine) so you could pretty much ignore line numbers, in fact by using a text editor and TYPEing the result into BASIC you could write code without them (the interpreter needed them, the TYPE trick made it put them in for itself).

But yes, this was uncommon so line numbers were a major thing.

And indentation was optional, you could add extra spaces to the start of lines and they would be kept and would have no effect on execution, but you would be wasting precious bytes of RAM and if using one of the heavier display modes (0, 1 or 2) you would only have 8.5Kbyte to play with for all the code and run-time storage (your variables, BASIC's call stack).