@Mcwong644
Please note that switching between mesh nodes is done by smartphone. Mesh (any mesh, not just Deco) can encourage or discourage that switch, but it is smartphone that decides, when.
That "when" is mostly based on how strong WiFi signal is. If signal from current node is "strong enough," whatever definition smartphone applies to that, it may not switch. So, the objective is to try lowering signal from Main node when you move close to Satellite node.
If you want to try suggestions I can provide below, first enable back in Deco App Fast Roaming and enable mesh setting for your smartphones. These are two settings that tell Deco encourage switch between nodes, disabling them discourages smartphone from switch. It still can, and will, but even less often.
Now, suggestions:
1. Disable 2.4GHz in your Deco WiFi network settings. Leave 5GHz band only. It provides less coverage, meaning when you get closer to Satellite Deco your Main Deco signal will be dropping faster, forcing smartphone to switch sooner.
2. Move Main Deco further away from Satellite Deco and room it is in. If they are, for example, sitting on 1st and 2nd floors above each other, and on top of that provide 2.4GHz network, smartphone will have little incentive to switch nodes.
Look at this picture from TP-Link mesh overview, see how two Deco nodes are located in the house. Second floor Deco is as far away from first floor Deco as possible.
You can also check Samsung smartphone forums or Samsung tech support for topics related to WiFi roaming. If there are configurable WiFi settings in Samsung device that will make it switch mesh nodes sooner, these will be related to WiFi signal measured in dBm. If you find where you could change dBm value for WiFi signal in smartphone settings, that most likely will be it.
Note that if you google WiFi roaming you might find Google Play Store apps that can tune this parameter. They did their job, but unfortunately in Android 9 and 10 they are no longer working - apparently, access to that configuration is now denied to third party apps. So, my point is: if you see such apps, don't bother installing them, they won't work on Samsung A50.
Finally, Deco app is really slow in reflecting device movement between nodes. As in "really, really taking its time to update that info." If you want to have real time status of which node your smartphone is connected to, install WiFi analyzer on your smartphone and use it to check. I use WIFIman from Ubiquiti, and can recommend it.