Your biggest obstacle is a lack of initiative. If you're always looking for a shortcut your work will suffer. If you want the best product you need to put in the work, and that will require at least a couple of software applications and possibly a converter. Put in the work and the reward will be more gratifying.
I write using LibreOffice Writer. It's free and handles image inserts better than Word. Once my manuscript is fully proofed and edited, I create one copy to format for paperbacks and import another copy into Calibre (the import process creates another copy in the Calibre folder). Calibre isn't the only ebook management and editing software out there, it happens to be the one I use.
When I create the original manuscript, I format text alignment, paragraphs, section breaks, page breaks, and chapter titles and numbers. These are the elements which both versions use.
When the doc is imported to Calibre it adds the code for the formatting already in place, so that part is mostly done. I convert to epub and clean up the excess gobbledygook, set my image sizing, and perform a few other tweaks. Then I validate the epub with ePub Check. Since ePub is the industry standard, this method leaves you with a functioning ebook before you ever submit it to distribution and retail sites. You can use it to proofread the book or give out to beta readers, or for promotion and review.
For paperback I perform the formatting specific to that version using the copy, including Page Styles (which are also easier compared to Word), Front Matter, Back Matter, Invisible Table TOC, Page Numbers, and alternating headers with the Author and Title so it looks like a book. Once the formatting is done I save the file, then also save it as a template, and finally I export it as a PDF directly from LibreOffice (that part does save having to use another program).
This certainly isn't the only way to do it, but it's the most efficient way I've found and my books look like books. If you're not offering paperbacks, simply eliminate that part, but you can;t get a quality book from one application.