Dual boot no option menu

I'm currently running ver 14393 (32) and tried installing 14986 (insider) on a partition. The install went ok but the installed version had some problems: repeated BSODs and really slow response. The hard part was getting back to my working version. I thought there was a boot menu to select which installation to boot to but none appeared. I finally booted from the install disk and found the boot choices there. What can I do to fix this problem?
tcebob

Add an entry to the boot menu using bcdboot.exe.

Open an admin cmd and type:

bcdboot 14393_partition_letter:\Windows

e.g.

bcdboot d:\windows

(then press enter)

@tcebob :
Could you get in to the new version?

The boot timeout could have faulted to 0, you may be able to change that by holding Shift while clicking Restart to access boot options.

To clarify: I could only boot to the new version. I found a program EasyBCD NeoSmart Technologies that makes bcdboot a bit easier. It's really confusing to have 2 operating systems named "Windows 10" but I managed to sort it out and renamed one to "Insider." Now that I know about shift/restart I think I'll opt out of the automatic menu.

Many thanks!

tcebob