There are two registers that all Spaniards living outside Spain have access to and that many people discover when they already need them. The first is the PERE, the Register of Spanish Residents Abroad. It is the basic registry of the Spanish Administration for citizens living outside the country. Registration is free, it is done at the corresponding consulate depending on where you live in Switzerland (Bern, Geneva or Zurich), and has no cost or generates new obligations. The second is the CERA, the Electoral Census of Absentee Residents, which is the one that allows voting in Spanish elections from Switzerland. To be in the WAX you have to be in the PERE first.
Why it matters to be registered: If you lose your passport or ID in Switzerland and go to the consulate, the process is significantly faster if you are already in the system. If there is an official Spanish notification that affects you, an inheritance, a process, something fiscal, the State has your address and can locate you. If you want to vote in Spain from here, you can't do it without WAX. And if you have children born in Switzerland, pre-registration of parents greatly simplifies the documentation of minors.
What many people don't know is that enrolling in the PERE has no effect on your situation in Switzerland. It does not affect your residence permit, it does not create any additional tax obligations, it does not generate any notice to the Swiss authorities. It is simply a Spanish database that registers its citizens abroad.
In the group there are people who have been here five, ten or fifteen years and have never done so. It happens. The problem is that when you need it, it's usually at a time when you don't have time to do it calmly.