To just replace '#' with a space we can use the replace function which replaces all occurrences of a specified text in a String with different text.
But from what I understand you wish to convert "forgot password #stoppingid.stoppingid error display #errorcodeid.errorcodeid #support4kid.support4kid ..." to "forgot password error display ..." or "forgot password stoppingid error display errorcodeid support4kid ..."
To accomplish this I would suggest that you use the "split" function to split the string into a list of words and use the "update_data" action to set it to a variable. You could then use the loop action to loop through those words in the variable and build another string of the words you want from that list (or perform further actions on the words, e.g. if they start with #).