My H1b got approved in 2021 from India and it got expired last month, I didn’t travel and didn’t go for stamping as well because my employer missed few experience letters.
Now I found another employer to transfer the petition and Is there any way to amend the exciting approved h1b to include all my experience.
There is no amendment in your case. The new employer have to file a new H1B petition however based on prior approval, they can request the petition under cap-exempt. There are chances that it may get approved under cap-exempt so you may not have to go for lottery process.
Yes, you can do amendment with your current employer and also have a change of employer petition in parallel. Both will be processed independently and if the chnlange of employer gets approved you have the option to either stay with your current employer or move to the new.