I just want to find a way to let Electrum cold wallet display more change address. A friend teach me a way to display more address by command wallet.storage.put('gap_limit', 50) and wallet.storage.write(). It's worked. There must be some command to display more change address. In lower version Electrum, I knew the commands , but I forgot now. And I did't find them in
http://docs.electrum.org/en/latest/.
use the Electrum console command:
wallet.create_new_address(True)
Passing a parameter of "True" to the create_new_address() function will generate a change addresss past the so-called "gap limit"
Note: if you want to generate "receive" addresses... then use "False" as the parameter:
wallet.create_new_address(False)
"True" and "False" are case sensitive... you need the uppercase T or F

You can even use a little "for" loop to generate a whole bunch in one go:
http://docs.electrum.org/en/latest/faq.html#how-can-i-pre-generate-new-addresses