Looking for how to use separate() with multiple separators in R (ClinVar variant data dealing)

Dear StackOverflow community

I'm a biologist and I'm working with a disease/genetic variants from ClinVar official database. My aim is to extract all gene names, transcripts and variants from this list.

ftp://ftp.ncbi.nlm.nih.gov/pub/clinvar/xml/ClinVarFullRelease_2020-01.xml.gz

However, ClinVar offers the information I need in a single column called "Name". (I've separated some of the values with different results that I want to deal with in the example in the table below:)

                                                           Name ClinicalSignificance
1                                        NG_012236.2:g.11027del           Pathogenic
2                    NM_018077.3(RBM28):c.1052T>C (p.Leu351Pro)           Pathogenic
3                                         NC_012920.1:m.7445A>G           Pathogenic
4                                                     m.7510T>C           Pathogenic
5 NC_000023.11:g.(134493178_134493182)_(134501172_134501176)del           Pathogenic

(there is other type of data, however since it does not contain the information I need I will treat it as garbage)

I am looking for a way to split the "Name" column in 3 other columns, using multiple separators. I've tried using "|" as part of my regex argument for multiple matches. However, for each time it works, sends the data that has already been separated to a column to the right. My code:

ClinVar_Clean <- separate(ClinVar_Clean, Name, into = c("Transcript","gene.var"),sep = "(?<=\\.[0-9]{1,2})[(]|(?<=[0-9]{3,16}\\.[0-9]{1,2}):|(?=[cmpng]\\.)")
ClinVar_Clean <- separate(ClinVar_Clean, gene.var, into = c("Gene","Variant"),sep = "\\):|(?=[cmpng]\\.)")

My result:

    Transcript  Gene   Variant ClinicalSignificance
1  NG_012236.2            <NA>           Pathogenic
2  NM_018077.3 RBM28                     Pathogenic
3  NC_012920.1            <NA>           Pathogenic
4                    m.7510T>C           Pathogenic
5 NC_000023.11            <NA>           Pathogenic

How the result should look like:

    Transcript      Gene   Variant                                                  ClinicalSignificance
1  NG_012236.2              g.11027del                                                  Pathogenic
2  NM_018077.3      RBM28   c.1052T>C (p.Leu351Pro)                                     Pathogenic
3  NC_012920.1              m.7445A>G                                                   Pathogenic
4                           m.7510T>C                                                   Pathogenic
5  NC_000023.11             g.(134493178_134493182)_(134501172_134501176)del            Pathogenic

I also tried to execute each separator individually, instead of shifting the data to the right, however it also overwrites the remaining data.

Please if anyone could help, appreciates!