"Legal register" is a familiar term for managers of certain legal domains, namely environment and health and safety. Legal registers are usually found in dusty reports, Excel spreadsheets, and web 1.0 platforms. They are tick-a-box solutions for management systems, which meet the requirements of international standards like ISO 14001:2015, and OHSAS 18001.
The domains of environment and health and safety are very site specific in nature. Typically an environmental manager will be responsible for the environmental legal compliance for a specific operation, which is often a site containing an operation like a factory, which has a clear boundary around its activities. The legal universe that such an environmental manager is responsible for is determined by the legal jurisdiction and the specific activities at that site. It would be irrelevant to include legal obligations that apply to other sites (where such sites may have different activities or be based on other legal jurisdictions). It could be said to the environmental manager, "this legal register filters all law, and makes only your law available to you. Don't worry about the law that applies to somebody else's job- it's irrelevant and excluded."
In the same way that knowing the location, and the specific activities of an operation, such as a factory, allows one to prescribe the relevant obligation imposing sections of regulations, such "factors of relevance" can be used to prescribe a very relevant legal register. For other domains of law, such as data protection and corporate governance, the factors of relevance are not site specific, but are still used to filter out the relevant legal obligations for any conceivable manager. For example, in the domain of data protection, if you are the European data protection officer responsible for compliance with data-protection regulations including GDPR over a number of jurisdictions, the factors of relevance would be those countries' legal jurisdictions, as well as the manners in which personal information is used or processed by your company. In order to do your job, you would need to know all that law - and not the law relevant to somebody else's job.
To date, using factors of relevance to filter and update the law relevant to any given manager's job has been a manual process compiled internally at the cost of precious time and accuracy, or by lawyers or consultants, as loss leaders with the same constraints. However, breakthroughs in legal technology has enabled the compilation of "job specific legal registers" for any legal jurisdiction, type of law, and business activity to happen in an automated, accurate and cost effective way. These new generation legal registers form the basis and enable knowing of relevant regulations. As we like to say at Libryo, now you know :-)