Use multiple accounts/app cloner primium
Btw i don't think this will work now as all banking apps require sms verification from registered number and putting 10 sims in 1 phone isn't possible
Yes, u can use multiple banking apps in one phone. If u mean of same bank then might not possible. But may I know what to manage in a bank account.? U can get statements to ur mail id. To check transactions. And u can always use net banking for other purpose like investments.
HDFC allows upto 3 different logins on single installation... (and they are switchable by swiping on login screen)
create a new user in you phone
or
https://f-droid.org/app/net.typeblog.s...er
and
https://play.google.com/store/apps/details?id=c...
if the app needs sim verification then sadly there is no proper working way without inserting sim
what you can do is try registering with a no longer working sim which can trigger otp registration or customer id login in some apps
would be better if you can mention which app you want to use and for what purpose
KG+ for sharing 
Are you planning to compete with RBI ?
Jokes aside, almost all smartphones have dual app/clone app feature. You can use them for 2nd app. But for 3rd and onwards you need third party apps. And god knows how much secure those apps are .
Cloning apps available in Samsung , realme , mi devices. Or use island like apps. But you need required sim in your phone. So it is advisable to use netbanking. But still most banks need 2FA this days to login like ICICI SBI etc. exception like HDFC etc. There is no proper solution to this issue.
create a new user in you phone
or
https://f-droid.org/app/net.typeblog.s...er
and
https://play.google.com/store/apps/details?id=c...
if the app needs sim verification then sadly there is no proper working way without inserting sim
what you can do is try registering with a no longer working sim which can trigger otp registration or customer id login in some apps
would be better if you can mention which app you want to use and for what purpose
yes mostly shelter is more secure open source alternate to island with some extra feature (though they are not that big of features).
if it worked with island or if you can do the verification for sbi app it should work with shelter.
you can also try insular
https://f-droid.org/en/packages/com.oasisfeng.i...
which is based on island but is a bit better since island has google analytics and is mostly not maintained.
If these apps don't work or you need proper isolation then better use multi profile option in android which is similar to same thing on windows or mac ( the user switcher thing you see at login)
also if your phone has builtin clone app feature then these are apps work nearly same as that so won't make a difference in that case
with insular apps probably be retained as it's based on island and shelter i think gives error that there is already a profile though i am not sure. you can try installing them they either will retain or so give error in setup either way existing setup won't be affected.
The difference is mainly around privacy and being foss. most people won't notice them
you can find one comparison here https://secure-system.gitlab.io/Insular/fa...ml
.
if you want more privacy and complete isolation use native profiles. while it requires switching and separate phone setup, benefit with profiles is once you switch; the other user gets frozen completely. while with the you always have the second version of app running along with cloned play services etc though they can be blocked to some extent using pause work app button in qs or launcher or via the given apps or third party stuff like greenify