“Loads and Chargers” in Victron’s diagram means exactly that, It could be also called “EVERYTHING except battery minus”. So it’s every device’s minus except battery - this is the only way Shunt knows what is happening on the way to battery.
The best practice is to use some kind of busbar - for example Victron’s . Here You could connect every minus, than by thick wire connect it to Shunt’s “Loads and Chargers” port. For system with only charger and inverter I would use Terminal stud and stack minuses from inverter and battery on one bolt of the “minus” Terminal, the wire to shunt on other bolt. The “plus” terminal could be used as nice place to positive wires to meet.
Of course, if the current is low, You could try to get by using ferrules made for two wires (not two separate ferrules!), but I won’t recommend it.
Tsu, you might want to learn the basics of parallel / series configuration before any physical connections take place.
Google it & learn, as asking if mppt & inverter are parallel is clearly having little or no comprehension of electrical principles.
Ps we all had to learn at some point, i learnt pre internet in parents garage as a kid blowing stuff up lol