No, there's no "merge" function, but it's really not hard to copy one filter, add an "or" to the end of the other one and paste the first one into it.
Or, some add-ons give you a JQL function for "issue in filter (<name other filter>)"
I don't know what you mean by "cross in backlog view"
They ask you to raise an enhancement request at https://support.atlassian.com/contact
But if you do, you'll find it closed as a duplicate. You would be better off voting on the existing ones in https://jira.atlassian.com - I'd expect to find them in the search https://jira.atlassian.com/issues/?jql=project%20%3D%20%22JIRA%20Software%20Server%20(including%20JIRA%20Agile)%22%20and%20text%20~%20%22quick%20filter%22%20and%20text%20~%20merge
Welcome to your weekly Jira Ops Early Access program update, where we’re sharing news and updates on Jira Ops progress as we work toward our 1.0 release. If you ever want to drop us feedback or ideas...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs