howto add externals with subversion tortoise client lower than 1.8

I had a problems adding externals for a QF-Test Testsuite to a subversion repository with Tortoise client 1.7 . In the Web I've found a post that special functionality to add externals to a svn repo were added first in version 1.8 . This seems to not be true. I have written down a navigation and dialog path how to get there even with tortoise client version 1.7 :

• right-click-(repository_name_B_dir) >> TortoiseSVN >> Repo-browser
• (dir) right-click >> Show properties
• New... >> Externals
• New... >> (Local path); (URL) svn://(ip_or_name_X)/(repository_name_A)/(subdir) >> OK
• OK >> (Log Message) >> OK
• OK

The situation may be as follows. You have a repo at svn://(ip_or_name_X)/(repository_name_A)/(subdir).. which you possibly did locally checkout to:d:\projects\(repository_name_A)
Now you want to bring this subdir as an external to another existing local checked out svn repo at:
d:\projects\projects_group_L\(repository_name_B)\(subdir)
Then the above steps will help you.

Feel free to ask if something seems not right or questionable.