I thought I'd share this solution as it is something that I've struggled with for some time and finally have it working.
Redirecting ordinary URLs using htaccess is not usually a problem but once the seo friendly features are enabled it becomes complex as the urls are extensionless and already being redirected.
For example, to redirect https://www.mysite/products/apples => https://www.mysite/products/pears you can use the following:
RewriteRule ^products/apples$ /products/pears? [L,R=301]
However, if you're using the seo friendly URL feature and you put this at the end of your htaccess, it won't work.
The answer to get it to work though is actually quite simple (and I can't believe I didn't work this out earlier):
[red]
Put it immediately BEFORE the ECT seo friendly redirects[/red], that is to say, before this:
[size=1]<IfModule mod_rewrite.c>
RewriteBase /
RewriteRule ^category/([^/.]*)/?$ /categories.php?cat=$1 [QSA,nc,L,B]
RewriteRule ^products/([^/.]*)/?$ /products.php?cat=$1 [QSA,nc,L,B]
RewriteRule ^manufacturer/?$ /categories.php?man=all [QSA,nc,L,B]
RewriteRule ^manufacturer/([^/.]*)/?$ /products.php?man=$1 [QSA,nc,L,B]
RewriteRule ^([^/.]+)$ proddetail.php?prod=$1 [QSA,nc,L,B]
</IfModule>[/size=1]
I wouldn't put it first though as you'll likely have some important redirects there for switching to www and https etc. Also make sure RewriteEngine On appears somewhere before your new redirects.
Steve