You can submit a new W4 to your employer any time you need to make changes. You can reduce withholding by adding deductions to line 4(b):
To know how much to enter in the Deductions section, use the IRS Tax Withholding Estimator and follow the instructions.
In the Income and Withholding step of the estimator you can account for multiple jobs, employment gaps, etc:
After going through the estimator they will show results with a projected refund and a slider you can use to adjust how much refund you want to get. Sliding that bar down from what it initially shows will bring up a section on how to adjust your withholdings that will instruct you on how to adjust your W4 and also a link to a partially-filled W4 you can use based on your results.