I just completed my qualification to Finnish qualification to electrical work supervision 3 (SP3), so I'll try briefly explain how it works here in Finland. Note that this list of requirements is not complete, there are fine details there and here but I'll try anyway.
Here in Finland there must be an assigned person, "sähkötöiden johtaja" in Finnish which can be roughly translated as "supervisor of electrical work", who is responsible of safety and related standards compliance for any work involving electronics or electrical work above 120 VDC or 50 VAC. Basically this supervisor is who is responsible for all who work under him/her and gets all the blame if something goes wrong, like somebody dies due to non-compliant electrical installation or unsafe device after repair work

Notification of the electrical/electronics work must be given in writing to Finnish Safety and Chemicals Agency (Tukes) and contact info of the supervisor is included.
However, electronics hobby and some simple stuff like putting together a single phase extension cord is exempt from above rule.
This supervisor must have a) suitable education and/or suitable & sufficient working experience under Tukes registered employer b) undergo an examination "Sähköturvallisuustutkinto" in Finnish which means "Examination of electrical safety", which consists of two parts, first one involves legislation and safety rules in electrical work and second part is about technical parts of electrical standards. There are three levels of examinations in increasing level of depth.
There are three levels of qualifications for electrical work supervisors. This level determines which kind of work is allowed under his/her supervision.
Level 3 (SP3) is the "entry level" and it basically allows working on any equipment or branch circuits in house below 1500 VDC or 1000 VAC, i.e. you can install something like extra outlet, electrical stove, heater or some other fixed device. This is the one to get if one wants to do e.g. equipment servicing or testing in-house designed mains powered stuff. This is the one I have personally.
Level 2 (SP2) is otherwise same but it allows for putting in a breaker panel or doing modifications to it in addition that it also allows one to be "käytönjohtaja" or "Supervisor of electrical system operations", at same voltage levels. This is typically for building electrical installers, but device design and servicing is also allowed.
Then the most generic level 1 (SP1) allows also high voltage stuff above 1 kV, like 20 kV metropolitan distribution or those things. Many larger buildings here have their own transformers from 20 kV to 400 volts (phase-to-phase, i.e. 230 VAC between phase and earth). In that case, owner of the house and therefore of the electrical equipment, there must be assigned supervisor of electrical system operations. Like at level 3 and 2, maintenance work is also allowed.
Note that those who do the actual work do not need to have this qualification but it is the responsibility of the supervisor to ensure that all workers know all relevant standards, working practices and know how to work safely.
Regards,
Janne