It seems to me that minimum election thresholds in Bulgaria, Slovenia, Czechia, Poland, Latvia, and Israel function to reduce risk of political gridlock due to fragmentation (which can compound political crises, as seen in eg Weimar-era Germany) but large numbers of very small parties in these countries can group themselves as electoral alliances to get over the threshold. The parliamentary representation of fragmented alliances exacerbates an unhealthy level of political fragmentation in Israel and Bulgaria, contributing to frequent political gridlock, crisis, and early elections in those two countries.
Electoral alliances intended to get member parties over an electoral threshold are not a feature of politics in New Zealand or Germanic countries such as Norway, Sweden, Iceland, Germany, and Austria. Do they have any specific laws/restrictions which disallow registering several small parties as a single electoral alliance for an election? If so, have such rules been considered and rejected for any reason by countries where fragmented alliances contribute to fragmented politics, such as Bulgaria?
(Appendix: I understand that constituent parties of the long-standing coalitions CDU-CSU in modern Germany and The Alliance in Sweden have always registered separately for elections, so they are not 'electoral alliances' in the way I am using the term and have never protected member parties from the risk of running afoul of the electoral threshold.)