You can generate proxies from certain region, which doesn't show in the drop down box, by editing the country code in the proxy username.
For example, with a username of gfeawer-zone-resi-region-in,you can change it into:
gfeawer-zone-resi-region-br
gfeawer-zone-resi-region-vn
gfeawer-zone-resi-region-us
…
to use the proxies in Brazil, Vietnam and USA.