Q: Should I withdraw my manuscript if the Editor cannot find reviewers?

Six months is a long time for finding reviewers. If the Editor has clearly stated that he is unable to find reviewers within this time, I don't think it is worthwhile to wait any longer. It would be advisable to withdraw your manuscript and submit it to another journal rather than waste any more time here.

To withdraw your paper, you need to write an email to the Editor informing him of your decision to withdraw and requesting a confirmation of the withdrawal. Do not submit your manuscript to another journal before you receive a confirmation of withdrawal from the Editor, as this can be considered as a duplicate or simultaneous submission. Additionally, once you receive the confirmation email, save a copy of it as proof of the completion of the withdrawal procedure.

A word of advice for you: When you submit your paper to the next journal, try to provide names of preferred reviewers. If the submission system does not have this option, ask the Editor if you can suggest reviewers. Since the current journal had difficulty in finding reviewers for your paper, there is a possibility that your paper is on a very niche topic, and the other journal might also have the same difficulty. It would speed up the process if you could identify a few preferred reviewers who have expertise in the field.