I use an Asus router & the problem you talk about not seeing devices - I assume under Network - is one I frequently experience.
I've tried various "fixes" but in the end I just added the devices in my network, which includes 3 NAS units , as Quick Access - ie "Pin to Quick Access".
There are rarely stupid questions.
I don't think you can add devices to Network as that's down to Windows to discover them.
As for mapping drives, I regularly map a specific folder on my devices, as in right click the folder & select Map network drive & for it to be permanent tick the box "Reconnect at sign-in". Job done. That folder can be a high level one like "Public" for example. I don't use ip addresses btw.
As I've said I've also added the devices , once I can see them , to Quick Access.
Hope that helps.
There is of course a simple reason why you cannot see other devices, your network connection has been set to Public and not Private.
Windows will prompt you when you first add a new wireless or LAN connection, and you are given the choice of a Public or Private connection. If you have accidentally chosen Public, then I think network discovery is turned off by default.
I didn't notice that you were on Windows 7 so obviously Quick Access is not an option.
Mapping as I've suggested should work OK though as I don't think that process changed from 7 to 10 that I'm on.
Not seeing devices under Network seems to me to be more of an issue in 10 than in 7 from what I can remember, although for today for me they're all there but tomorrow who knows!
For my networked devices I always set the ip address within the device and then add it as manual/pre-assigned within the router. Where you do that in an HH I don't know.
There was an issue with Synology devices not being seen properly because of SMB3 and that support needed to be disabled in Windows, not sure if this was a Synology issue or Windows but I've added commands for that if that helps:-
sc.exe config lanmanworkstation depend= bowser/mrxsmb10/nsi
sc.exe config mrxsmb20 start= disabled
Drive mapping on Windows 7, dues not usually automatically reconnect on a restart, that is my experience. I have two machines, my main one on Windows 7 Pro, and another on Windows 10 Pro.
One workaround is to use the subst command and assign a drive letter, to a physical path, but that has to be done in a startup batch file, but works every time.
I use a TP Link router and also give all devices fixed IP addresses.