There is no way to lengthen the rise of pants unless you add a piece of fabric. You can't make longer what is not there. Of course you would have to put in a new zipper too. You could start with a larger longer pair of pants and rip them apart and make a pair to fit you using the pieces but that sounds like more work than making a pair from scratch with new material.

I did a lot of what you call refashioning when I was young to save money and that's the only reason I would do it

Thank you for your answer. I guess there is no magic bullet! But I thought I'd check to see if anyone had any suggestions.
I am finding that refashioning is improving my sewing skills, and if I make a mistake/don't like the end result on a thrifted or old piece of clothing the fact that there is minimal financial loss IS appealing.
Some things you just can't get any other way - as is true of sewing from scratch. Like these shoes I recovered with fabric. Not sewing, but it is fabric and I made a pattern. Some people sew around the bottom before gluing. I definitely can't buy them anywhere!

Some of the things we used to do in the 70s to save favorite jeans were adding contrast or print to the hems, making appliques to patch holes, making button holes(or grommets if you had the tools)to replace zippers and using shoelaces for closure. To change straight-legged pants to flared, we'd split the outside leg seam 10"-12" up and add contrast or print fabric to the space.
I never did this(but seems do-able to me), but could you replace the waistband with a wider one and add buttons or snaps(or as you mentioned, a longer zipper)and co-ordinate the fabric with bands to lengthen the hems?

A wider waistband is a good idea, thanks.
Kathy

I can tell you how to get a little more room in the rise, but the legs will still be too short. Put your hand down the right leg, all the way to the hem. Grab the hem of the left leg,and turn the whole garment inside out (left leg inside the right leg)

You now have a view of the crotch curve. Starting at nothing at the zipper on the front, draw a new, lower curve that merges into the center seam maybe one quarter of the way up the back center seam.

Thanks Eva, I will definitely try this.
Kathy

Yes you can lengthen the rise...meaning lowering the crotch. You can't raise the crotch, meaning shortening the rise as that means adding more fabric.

That is an interesting point. Shortening is the one that would take more fabric. I don't have a pair to try lengthening on right now. Haven't found any that I want to at thrifts when I have gone. I did buy a pair of what looks like men's pants in a cool fabric. Already has a long enough rise but otherwise too big. I'm just desparate for pants to wear to work.
If I have any luck one of these days I'll let you all know.
Thank you again for helping me think about this.
Kathy

My favorite comfy pants have wide stretchy waistband almost like sweat pants. Since i always wear my shirts out, I would be tempted to do this to other pants.

I alter patterns to do similar things. Never tried on pre-made, BUT

I have never in my life had pants truly fit. Discovered my crotch/inseam measurement is off their chart. So I take a pattern and I find the difference. I then add over the top of the pattern and use the pattern with further adjustments. My front addition was less than my back. To align the sides I would put small gathers on the back pieces. Seam up as usual

So the wider waistband should work for a simple alteration. New zipper or just add a fun over zipper closure (grommets, buttons, a pass thru placard with a loop for a lock--think treasure chest lock). If more length is needed in one half than the other some side seam reworking might be needed.