Changing the Display Name of that Row Action is not currently possible via customization, as Nextworld logic blocks currently reference row actions by that attribute and would break if it were changed. There is a backlog idea to change that and I am tagging this post to it.
An alternative worth exploring might be to hide that Row Action via an app setting or similar, and then via an extension app or customization of ManualChecksHeader, add a copy of that Row Action with the desired name.
Hi, this is not a renaming of the “preview check” but to replace “preview check” link with workflow “post check” when the page loads
Post check is a workflow which comes in the dropdown once the record is saved in draft status.
Now we want that in place of preview check.
Got it, I misunderstood the initial ask. As far as I know this is not possible. The best I can come up with is hide the Preview Checks row action in which case that menu will show 
Actions and then the first option in the list would be Prepare Checks (which may be renameable to Post Check per the ask). I don’t think there’s a way to show a Workflow Action in place of Actions.
Thanks for the response, can we like add “post check” before the record is in draft state and make it visible as soon as a user create a record
Also I don’t see any “prepare checks” maybe wrong app. For me it is “post checks”
You may be seeing Post Checks instead of base product behavior where it is Prepare Checks due to a customization of the FinancialsWFActionPrepareChecks action label data item.
It is not possible to expose the available workflow manual transitions until the record has undergone its first save. What might work for you situation though is, via a workflow extension, automate that the Post Checks manual transition in certain circumstances so the user never has to select Post Checks manually.