I have cancelled my 2nd home phone line recently. I have multiple phone jacks in home that are connected to cancelled 2nd phone line. Instead of rewiring all 2nd line jack to 1st,
Can I simply connect the 2nd line wire to 1st line at NID box.

I have orange/white to 2nd line and blue/while to 1st line. Would it be OK to double these wires on 1st line.

Thanks for any advise .

A better choice would be to move the lines, so you'll end up with an empty red/grn screw.

You'll end up with

Wht/blu and wht/or attached to green of line #1

Blu/wht or/wht attached to red of line #1

If the initial change was done with L1,L2 and L1+L2 adapters, then just moving the phone to a different jack would be all that's required.

Sounds good to move orange/white to blue/white, and white/orange to white/blue at phone box.